Thermally bonded viral barrier composite

ABSTRACT

A viral barrier composite of a thermoplastic film thermally bonded on at least one side thereof to a breathable thermoplastic web, and method for making the same. The viral barrier composite has viral barrier properties, a moisture vapor transmission rate of at least 700 g/m 2  /24 hours and a bond strength between the thermoplastic film and breathable thermoplastic web of at least 0.07N/cm. The viral barrier composite is formed by calendering an assembly comprising a thermoplastic film and a breathable thermoplastic web between a smooth roll and a pattern roll. The viral barrier composite may be used for constructing articles of protective apparel.

This is a division of application Ser. No. 08/415,530 filed Apr. 4,1995, now abandoned.

FIELD OF THE INVENTION

The present invention is directed to a thermally bonded viral barriercomposite, and a method of manufacturing the same.

DESCRIPTION OF THE RELATED ART

Surgical gowns, drapes, masks, gloves, sterile wraps, wound dressings,waste disposal bags, and other medical products require viral barrierproperties combined with breathability. Liquid repellency is recognizedas an important property in assuring that these products act as abarrier against the passage of bacteria or viruses carried in liquids.For example, body liquids and other fluids can permeate through asurgical gown or drape lacking liquid repellency properties. In additionto being liquid repellent and a bacteria and viral barrier, it has beenwidely recognized that these products must be breathable to becomfortable to the wearer. Water vapor from perspiration should betransmitted from inside to outside of the material so that the naturalevaporative cooling effect can be achieved. For example, in a continuousfilm of hydrophilic material, water vapor is effectively transportedthrough the film on a molecule by molecule basis.

One type of material commonly used for protective clothing is made froma nonwoven substrate calendered at high temperature and pressure. Whilehaving reasonable properties for protection, these garments are known tobe very uncomfortable due to their inherently low moisture vaportransmission and low air permeability characteristics.

A microporous membrane with viral barrier capabilities and breathabilityis described in U.S. Pat. No. 5,260,360 to Mrozinski et al. Mrozinskidiscloses a polymeric microporous membrane having a matrix of poresforming continuous passages through the thickness of the membrane andopening on the opposite surface thereof. The addition of fluorochemicalto the microporous membrane reduces the surface energy of the membrane,thereby increasing the numerical difference between the surface energyof the membrane and liquid contaminants.

The comfort and durability of microporous membranes, such as themembrane disclosed in Mrozinski, or other breathable viral barrier filmscan be significantly enhanced by laminating the membrane to suitablereinforcing webs, such as spunbond webs. However, the laminating processmay compromise the viral barrier capabilities or breathability of themicroporous membrane. For example, use of an adhesive to laminate areinforcing web to a microporous membrane can be problematic where theadhesive contains solvents reactive with the microporous membrane.Additionally, the solvents in some adhesives present environmentalhazards, which increase the cost of the product.

Thermal or ultrasonic bonding of a microporous membranes may createpinholes in the membrane and diminish the viral barrier capabilities.Thermal or ultrasonic bonding may also collapse the micropores andunacceptably reducing the breathability and moisture vapor transmissionproperties of the webs.

One possible reinforcing web is a bonded spunbond web, which ismanufactured by calendering unbonded spunbond fibers to form a tightermatrix of fibers that is smooth, soft and abrasion resistant. Previousattempts to thermally bond a 34 grams/m² (1 ounce/yd²) bonded spunbondweb to a microporous membrane using a heated point-bonding roll(approximately 15% point contact) and a heated smooth roll calenderingroll (nip gap 0.002 to 0.0508 mm) resulted in an unacceptably low bondstrength in the range of 0.012 to 0.018N/cm.

Alternatively, unbonded spunbond may be used for the reinforcing web.Unbonded spunbond is essentially extruded thermoplastic fibers depositedonto a moving belt that are allowed to harden without performing acalendering operation. Unbonded spunbond, while exhibiting good bondingcharacteristics, has low tensile strength. Additionally, unbondedspunbond webs have a coarse finish which is both uncomfortable to wearand provide minimal resistance to abrasion.

A related problem exists with regard to creating seams for assemblingprotective apparel that are both strong and resistant to thetransmission of viral pathogens. For example, the strength of sleeveseams and sleeve attachment seams on surgical gowns is critical due tothe significant stresses encountered by sleeves during use.

Protective apparel containing sewn seams can have needle holes whichgreatly reduce the effectiveness of the viral barrier in the seam area.Thus, bacteria and viruses, such as the immunodeficiency virus orHepatitis B virus, which may be present on the surface of the protectiveapparel, can be transmitted through the needle holes. One approach tocreating viral resistant seams includes interposing an elastomericmaterial between the overlapping fabric at the seam. The highlyresilient nature of the elastomeric material causes it to return to itsoriginal position after the sewing needle is removed, so as to provide abetter barrier to viral pathogens.

Ultrasonic welding has also been used to produce less permeable seamsfor protective apparel. However, some ultrasonic welding techniquescreate seam structures that lack the tensile strength necessary forcertain protective apparel, requiring a secondary reinforcing operation,such as the application of a viral barrier adhesive tape over the seam.

The V-shaped ultrasonic welding wheel 10 and ultrasonic generator 15 ofFIG. 1 provides a thin, comfortable weld for use in protective apparel.The sloped welding area 11 cuts and seals the seam at the edge of thewheel 10. However, the small surface area and sloped configuration ofthe welding area 11 produces a relatively small quantity of moltenthermoplastic material so that welding speed is generally reduced forseams of acceptable tensile strength.

Alternatively, the ultrasonic welding wheel 12 shown in FIG. 2 relies ona relatively large solid seal area 13 and intermittent feed notches 14to produce a greater quantity of molten thermoplastic material. Thelarge solid seal area 13 allows the welding wheel 12 to achieve higherspeeds. However, the feed notches 14 of the weld wheel 12 of FIG. 2creates an intermittent row of seal lines or a stitch patterns adjacentto the solid seal weld line. The resulting seam has a width "w" which isgenerally stiff and uncomfortable to wear.

SUMMARY OF THE INVENTION

The present invention is directed to a viral barrier composite, andmethod for manufacturing the same. The composite may be used for avariety of protective apparel, such as surgical gowns, drapes, masks,gloves, sterile wraps, wound dressings, waste disposal bags or otherproducts requiring viral barrier properties.

The viral barrier composite is formed by thermally bonding athermoplastic film on at least one side thereof to a breathablepolymeric web. The resulting composite has viral barrier properties anda moisture vapor transmission rate of at least 700 g/m² /24 hours. Thebond strength between the polymeric film and thermoplastic web is atleast 0.07 N/cm (0.04 lbs/inch). The composite has an air permeabilityexpressed as Gurley porosity of less than 1000 seconds/50 cc, andpreferably less than 500 seconds/50 cc. The breathable thermoplastic webmay be woven or nonwoven fibrous materials made of poyolefins,polyethylene, polypropylene, polybutylene and combinations thereof.

In one embodiment, the polymeric film is a thermoplastic polymer and awater- and oil-repellent fluorochemical compound that forms amicroporous membrane with oleophobic and hydrophobic properties. Lessthan 100 viruses, preferably less than 10 viruses, and most preferablyno viruses are permitted to pass through the viral barrier compositeaccording to ASTM Test Method ES 22-1992. The microporous membrane ispolypropylene and the thermoplastic web is a bonded spunbond nonwovenpolypropylene web.

The present invention is also directed to an article of protectiveapparel constructed from the viral barrier composite. The article ofprotective apparel may have at least one reinforced viral resistantseam. The viral resistant seam includes a first viral barrier compositehaving a first attachment edge and a second viral barrier compositehaving a second attachment edge arranged with the first composite viralbarrier to form a common seam edge extending along the first and secondattachment edges. At least one reinforcing strip constructed from athermoplastic material extending along the common seam edge is thermallybondable with the first and second viral barrier composite. Anultrasonic weld bonds the first and second attachment edges and thereinforcing strip extending along a seal edge to form the reinforcedviral resistant seam.

The present invention is also directed to a process for thermallybonding a viral barrier composite by calendering an assembly of athermoplastic film and a breathable thermoplastic web between a smoothroll and a pattern roll so that the bond strength between thethermoplastic film and thermoplastic web is at least 0.07N/cm and theresulting composite has viral barrier properties and a moisture vaportransmission rate of at least 700 g/m² /24 hours. In the preferredembodiment, the thermoplastic film is positioned to contact the smoothroll and the breathable thermoplastic web is positioned to contact apattern roll.

The surface speed of the smooth roll and pattern roll at a nip point maybe between 3-200 meters/minute, and preferably between 20-100meters/minute. The temperature of each calendering roll is in the rangeof approximately 100°-200° C. The pressure at a nip point between thesmooth roll and the pattern roll is approximately 5-50 N/mm. The patternroll has a percent bonding surface area of approximately 7-30%, andpreferably between 15-25%. In an embodiment where the pattern roll is apoint bonding roll, the density of the bonding points on the pointbonding roll is approximately 1.75 to 150 points/cm². The surface areaof the bonding points on the point bonding roll is about 4.0-0.20 mm².The air permeability expressed as Gurley porosity is less than 1000seconds/50 cc, preferably less than 500 seconds/50 cc, and mostpreferably less than 200 seconds/50 cc.

The process also includes forming a viral resistant seam between twosheets of the viral barrier composite. First and a second attachmentedges of a first and a second viral barrier composites, respectively,are arranged to form a common seam edge. A reinforcing strip ispositioned to extend along the common seam edge. The reinforcing stripis constructed of a thermoplastic material thermally bondable with thefirst and second viral barrier composites. An ultrasonic weld is formedalong a seal edge to connect the first and second attachment edges andthe reinforcing strip, so that the viral resistant seam is formed. Theultrasonic welding wheel has a cutting edge immediately adjacent to awelding surface and an ultrasonic generator. The continuous surface ofthe weld wheel extrudes molten thermoplastic material into the fibers ofthe spunbond laminate adjacent to the viral resistant seam.

The present invention relates to a reinforced ultrasonic seam forprotective apparel that resists the transmission of viral pathogens, anda method of manufacturing the same. The viral resistant seam has a lowsurface area and a high tensile strength that increases comfort andfunctionality.

In a first embodiment, the reinforced viral resistant seam forprotective apparel includes a first and second webs arranged to form acommon seam edge extending along first and second attachment edges. Atleast one reinforcing strip constructed of a material thermally bondableto the webs is arranged along the common seam edge. An ultrasonic weldis formed along the common seam edge. The ultrasonic weld line islocated immediately adjacent to the seal edge to create a low surfacearea reinforced viral resistant seam.

The reinforced viral resistant seam may be useful with a variety ofmaterials, such as poyolefins, polypropylene, polyethylene,polybutylene, copolymers and combinations thereof, and the present viralbarrier composites. The first and second webs may be a variety ofthermoplastic polymers, such as a bilaminate or trilaminate compositesconstructed from a polypropylene microporous film laminated topolypropylene spunbond nonwoven fiber. The reinforcing strip may also bea thermoplastic material, such as polypropylene.

The present low surface area reinforced viral resistant seam may be usedto assemble any seam of the protective apparel, although it isparticularly useful for attaching sleeves to the body portion of asurgical gown.

The method for forming a low surface area reinforced viral resistantseam includes arranging a first and second webs to form a common seamedge extending along the first and second attachment edges thereof. Atleast one reinforcing strip is positioned along the common seam edge.The reinforcing strip(s) preferably includes a thermoplastic materialthermally bondable with the thermoplastic material contained in thefirst and second webs. An ultrasonic weld is formed along a seal edge.

The step of forming an ultrasonic weld includes passing the common seamedge of the reinforcing strip and webs between an ultrasonic weldingwheel and an ultrasonic generator. One embodiment of the ultrasonicwelding wheel includes a weld surface generally parallel to the plane ofthe reinforcing strip and webs and immediately adjacent to a cuttingedge.

The welding wheel permits feeding the present viral barrier composite atrates of approximately 12.0 meters/min. The weld area extrudes moltenthermoplastic material into the fibers of the spunbond laminate. Thecritical dimension between the welding surface and ultrasonic generatoraffects the degree to which the fibers laminated to the viral barriercomposite near the weld area are weakened and the quantity of moltenthermoplastic material produced by the ultrasonic process. If thecritical dimension is too small, the fibers near the weld degrade,weakening the seam. Alternatively, if the critical dimension is toolarge, an insufficient quantity of molten thermoplastic material will beproduced by the welding process, resulting in a weak seam.

Definitions as used in this application:

"Bilaminate" means a microporous membrane or other breathable filmlaminated on one side thereof to a woven or nonwoven web. For example,spunbond polypropylene nonwoven web laminated to a polypropylenemicroporous membrane.

"Critical dimension" means the distance between the solid seal area ofthe welding wheel and the ultrasonic generator.

"Hydrophobic" describes materials which are not wet by liquid water oraqueous body fluids and which are capable of repelling and preventingthe passage of liquid water through their structure.

"Heat sealable" is used herein to describe materials having athermoplastic component that can be sealed together using a hot bar,ultrasonic, or other thermal process sealer.

"Moisture vapor permeable" is used herein to describe materials whichreadily permit the passage of water vapor through the membrane but donot allow the passage of liquid water.

"Oleophobic" describes materials which are not wet by oil, grease, orbody fluids, which contain oily components, and are capable ofpreventing the passage of oils and grease through their structure.

"Bond strength" means the force required to delaminate a multilayeredmaterial.

"Protective apparel" means surgical gowns, drapes, masks, gloves,sterile wraps, wound dressings, shoe covers, neck gaiters, sleevecovers, waste disposal bags, or other products requiring some viralresistant or barrier properties.

"Thermoplastic" means a polymeric material having a thermoplasticcomponent which may include polyolefins, polyesters, polyetheresters,and polyamides. Examples of suitable thermoplastic polymers include, byway of illustration only, such polyolefins as polyethylene,polypropylene, poly(1-butene), poly(2-butene), poly(1-pentene),poly(2-pentene), poly(3-methyl-1-pentene), poly(4-methyl-1-pentene),1,2-poly-1,3-butadiene, 1,4-poly-1,3-butadiene, polyisoprene,polychloroprene, polyacrylonitrile, poly(vinyl acetate), poly(vinylidenechloride), polystyrene, and the like; such polyesters as poly(ethyleneterephthalate), poly(tetramethylene terephthalate),poly(cyclohexylene-1,4-dimethylene terephthalate) orpoly(oxymethylene-1,4-cyclohexylenemethyleneoxyterephthaloyl), and thelike; such polyetheresters as poly(oxyethylene)-poly(butyleneterephthalate), poly(oxytrimethylene)-poly(butylene terephthalate),poly(oxytetramethylene)-poly(butyleneterephthalate),poly(oxytetramethylene)-poly(ethylene terephthalate), and the like; andsuch polyamides as poly(6-aminocaproic acid) or poly(,-caprolactam),poly(hexamethylene adipamide), poly(hexamethylene sebacamide),poly(11-aminoundecanoic acid), and the like.

"Trilaminate" means a microporous membrane or other breathable filmlaminated on both side thereof to a woven or nonwoven web. For example,spunbond polypropylene nonwoven webs laminated to a polypropylenemicroporous membrane.

"Water repellent" describes materials which are not water wettable andare capable of preventing the passage of liquid water through thematerial by capillary action under varying ambient atmosphericconditions, including water impinging on the surface of the membrane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a prior art V-shaped weld wheeldesign;

FIG. 2 is a schematic illustration of an alternate prior art weld wheeldesign;

FIG. 3A illustrates a method for manufacturing a thermally bondedbilaminate viral barrier composite;

FIG. 3B illustrates an alternate method for manufacturing a thermallybonded bilaminate viral barrier composite;

FIG. 3C illustrates a method for combining the step of bonding spunbondfiber with forming a thermally bonded bilaminate viral barriercomposite;

FIG. 4 illustrates a method for manufacturing a thermally bondedtrilaminate viral barrier composite;

FIG. 5 is a sectional view of an exemplary pattern roll for use inmanufacturing a thermally bonded viral barrier composite;

FIG. 6 is a front view of the calendering rolls of FIG. 3;

FIG. 7 is a schematic illustration of a low surface area reinforcedviral resistant seam;

FIG. 8 is a schematic illustration of an alternate low surface areareinforced viral resistant seam;

FIG. 9A is a schematic illustration of an apparatus for creating areinforced viral resistant seam;

FIG. 9B is a schematic illustration of an alternate apparatus forcreating a reinforced viral barrier seam used for testing the presentwelding concept on a variety of materials; and

FIG. 10 is an illustration of an exemplary surgical gown with reinforcedviral barrier seams.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to a thermally bonded viral barriercomposite, and a method for manufacturing the same. The viral barriercomponent of the present viral barrier composite may include variousfilms or microporous membranes with viral barrier properties, such as amonolithic film sold under the tradename Hytrel from E. I. duPont deNemours and Company of Wilmington, Del. or a microporous membranedescribed in U.S. Pat. No. 5,260,360 to Mrozinski et al., which ishereby incorporated by reference.

Microporous membranes useful in the present invention may have amicroporous structure generally characterized by a multiplicity ofspace, separated, randomly dispersed, nonuniform shaped, equiaxedparticles of polyolefin connected by fibrils which are intimatelysurrounded by the processing compound and the fluorochemical. Themicroporous membrane is preferably liquid repellent, moisture vapor andair permeable and has viral barrier capabilities. The viral barriercharacteristics of the microporous membrane described in U.S. Pat. No.5,260,360 to Mrozinski et al., are disclosed in PCT application No. WO93/07914 published on Apr. 29, 1993 and U.S. patent application Ser. No.08/384,079 entitled A METHOD FOR PREVENTING TRANSMISSION OF VIRALPATHOGENS, filed Feb. 6, 1995, which is hereby incorporated byreference.

The strength and durability of many microporous membranes and otherviral barrier films may be increased by laminating the membrane or filmto a suitable substrate or web. Additionally, if the membrane or film isused for protective apparel, the substrate or web can enhance comfortfor the wearer. For example, a suitable substrate may be a web of wovenor nonwoven thermoplastic fibers.

Suitable fibrous non-woven webs include ethylene-propylene copolymer,high density polyethylene, low density polyethylene, linear low densitypolyethylene, polyamides, polyesters, a blend of polypropylene andpolybutene, and a blend of polypropylene and linear low densitypolyethylene, although it will be understood that various woven andnonwoven webs may serve this purpose. In the embodiment discussed below,the reinforcing substrate is at least one layer of a bonded spunbondnonwoven polypropylene web. The fibers of the bonded spunbond web havean average diameter of approximately 20 micrometers and the spunbond webhas an average weight of 34 grams/m² (1 ounce/yard²), although spunbondin the range of 14-68 grams/m² (0.4-2.0 ounce/yard²) may be used. Abonded spunbond nonwoven polypropylene web suitable for lamination tothe polypropylene microporous membrane may be obtained from Poly-Bond,Inc., of Waynesboro, Va.

The present thermal bonding process represents a balance of variousfactors, including maintaining an adequate bond strength between theweb(s) and the microporous membrane or viral barrier film, minimizingpinholes that decrease viral barrier capabilities and minimizing thecollapse of micropores that decreases breathability and moisture vaportransmission rate.

FIG. 3A is a schematic illustration of a calendering system 20 forlaminating a web 22 to a microporous membrane 24 using heat, pressureand a pattern roll 26. The web 22 and microporous membrane 24 movebetween the heated metal pattern roll 26 and a heated metal smooth roll28 in the direction of the arrows. Alternatively, the smooth roll may berubber or some other resilient material heated by an external source.The surface speed of the rolls 26, 28 are approximately the same at thenip point 30. The spunbond web 22 is preferably interposed between themembrane 24 and the pattern roll 26, although it will be understood thatthe arrangement of the materials 22, 24 may be reversed.

The resulting bilaminate viral barrier composite 48 has a matrix ofpoint bonds 42 and indentations 44 corresponding to the pattern of pointsources 40 on the pattern roll 26 (see exemplary point bonding roll ofFIG. 5). In an embodiment where the web 22 is a spunbond nonwoventhermoplastic material, the fibers of the spunbond web are compressedand extruded under the point sources 40 and converted into a non-porousfilm. The micropores (not shown) in the microporous membrane 24 at thepoint bonds 42 are generally collapsed. The point sources 40 generallyextend into the microporous membrane 24, compressing the microporousmembrane and forming corresponding, although generally smaller,indentations 45 on the opposite side of the viral barrier composite 48.

The gap between the rolls 26, 28 may either be fixed or maintained as afunction of the pressure "P" on the viral barrier composite 48. FIG. 3Billustrates the calendering system 20 configured so that the gap betweenthe rolls 26, 28 is determined by the pressure "P" between the rolls 26,28 and the resiliency of the viral barrier composite 48. It will beunderstood that the configuration of FIG. 3B may also be used to form atrilaminate viral barrier composite 49 or various multilayeredcomposites.

FIG. 3C is an alternate embodiment in which unbonded spunbond fibers 32extruded onto a moving support structure 33 are calendered to the viralbarrier film 24 between a heated pattern roll 26' and a heated smoothroll 28'. It will be understood that this embodiment essentiallysimultaneously bonds and laminates the unbonded spunbond fibers 32 tothe viral barrier film 24.

FIG. 4 is a schematic illustration of a thermal calendering system 20"for creating a trilaminate viral barrier composite 49. The system 20"simultaneously laminates webs 22a, 22b to opposite sides of themicroporous membrane 24. As discussed in connection with FIGS. 3A and3B, the pattern roll 26 compresses the webs 22a, 22b, and microporousmembrane 24 at point bonds 42", creating a matrix of indentations 44",45" in the viral barrier composite 49. It will be understood that thepresent method and apparatus for creating a viral barrier composite isnot limited to composites of two or three layers. For example, acomposite with four or more layers alternating between microporousmembrane 24 and web 22a, 22b may be desirable for some applications.

FIG. 5 illustrates in the exemplary point bonding roll 26 having apattern of grooves 50, 52 machined or etched into the outside surface ofthe roll 26. The grooves 50, 52 create a plurality of diamond shapedpoint sources 40 for use in the calendering systems 20, 20' discussedabove. It will be understood that the present invention is not limitedby the particular shape or arrangement of the point sources 40 and thata variety of continuous or intermittent relief patterns on the roll 26are possible.

The micropores in the membrane 24 are generally collapsed by the pointsources 40 at the bonding points 42, 42". Additionally, the viralbarrier composite is stiffened at the bonding points. Therefore, thepercent bond area on the point bonding roll 26 preferably is minimized,while maintaining adequate bond strength. The point sources 40 generallyencompass between 7-30% of the total surface of the pattern roll 26.Additionally, in order to minimize point pressures which create pinholesin the microporous membrane 24, the density of point sources 40 is onthe order of 1.75/cm² to 150 points/cm² with an average point size ofapproximately 4.0 to 0.20 mm², respectively.

The uniform nip pressure, line speed and roll temperatures are criticalto maintaining the integrity of the viral barrier by minimizingpinholes, minimizing damage to the breathability of the microporousmembrane, and creating a composite material with adequate bond strength.Although the interrelation of these parameters will be discussed indetail below, line speed may be in the range of 3-200 meters/minute andgenerally 20-100 meters/minute, with roll temperatures in the range of100°-200° C.

FIG. 6 illustrates the difficulty of maintaining uniform nip pressureacross the complete width of the rolls 26, 28. In particular, whenforces "F" are placed on opposite ends of the rolls 26, 28, a bendingmoment "B" is created such that the pressure along the nip point 30 maydecrease in the center portions 26a, 28a of the rolls 26, 28. Rollscapable of creating a uniform pressure of 5-50N/mm across the nip point30 are available from New Era Converting Machine, Inc. of Hawthorne,N.J.; Webex, Inc. of Neenah, Wis.; Kusters of Spartanburg, S.C.; B. F.Perkins of Chicopee, Mass.; and Ramisch (Greenville Machinery Corp.) ofGreer, S.C.

In evaluating the materials of the present invention and the comparativematerials, the following test methods were used.

Bond Strength

Bond Strength was measured using an "Instron Model 1122 Tensile Tester"for Examples 4-6 and Comparison Examples C, D, F or "Instron Model 4465Table Mounted Universal Testing Instrument" for Examples 2, 3, 5, 7, and8 from Instron Corporation, Canton, Mass. or "Hounsfield H10KM UniversalTesting Machine" for Example 1 and Comparison Examples A-B fromHounsfield Test equipment, Croydon, England. The gage length was set at25 mm and the crosshead speed was 304 mm/min. A sample was cut from thebilaminate or the trilaminate 25 mm wide and approximately 127 mm long,in the machine direction. The delamination of the sample was initiatedby hand to insure that delamination would occur. The ends of the samplewere clamped into the jaws of the instrument and mechanically separatedat a 180° peel. The average separation value was recorded from the chartrecorder for the distance of the bond. The mode of failure was recordedas peel, elongate, delaminate, or tear. For trilaminates, both bondsites were tested.

Porosity

Porosity was measured according to ASTM-D726-58 Method A and wasreported in Gurley seconds required for 50 cc of air to permeate 6.5 cm²(one square inch) of fabric. Gurley is a coarse screening test usedprior to the more expensive MVTR or Viral Penetration tests discussedbelow.

Pinhole Test

The number of pinholes were counted using a method generallycorresponding to modified ASTM ES 21-1992. Modification includes using alarger test area, 50.8 cm². The presence of pinholes in fabric orplastic film for 50.8 cm² area was determined using a test fluid at0.0138 MPa (2 psi) for 60 seconds.

Moisture Vapor Transmission Rate (MVTR)

Moisture vapor transmission rates (MVTR) were made using ASTM-E96-80Upright Water Method, low humidity on one side and high humidity on theother. A 100 ml glass jar with a 3.81 cm diameter hole centered in ascrew-on cap was filled with 50 ml of water. Three 38 mm diametersamples were die cut from the composite area. Each sample was centeredover the adhesive side of a 5.07 cm² area hole of a foil adhesive ring.The sample and foil ring hole were lined up with a second foil ring witha 5.07 cm² area hole forming a foil/sample/foil assembly that was flat,wrinkle-free and that had no void areas in the sample area. A 4.445 cmdiameter rubber washer was placed on the jar lid. The foil/sample/foilassembly was placed on the rubber washer with the film side of thesample up. The screw on cap was placed loosely on the jar. The jarscomplete with assemblies were placed in a constant temperature andrelative humidity chamber for four hours at 40° C.±1° C. and 20±2percent relative humidity. The screw on cap was tightened so that samplematerial was level with the cap and the rubber washer was seated. Thejars were removed from the chamber after four hours and weighed to thenearest 0.01 gram (W₁ =initial weight). The jars were returned to thechamber for at least 18 hours. After at least 18 hours the jars wereremoved from the chamber and weighed again (W₂ =final weight). Themoisture vapor transmission rate in grams/meter² in 24 hours wascalculated for each sample using the following: ##EQU1## The threereadings for each sample were averaged and reported to the nearest gram.

Resistance to Viral Penetration by a Blood-Borne Pathogen

The viral barrier properties of a composite was determined by ASTM TestMethod ES 22- 92. Basically, this test indicates whether avirus-containing liquid penetrates the test material. A test pressure of13.8 kPa (2 psi) is applied throughout the liquid to the test material.The non-liquid-containing side of the test material is then swabbed andthe swabbed exudate is cultured for 24 hours. The number of viruses isthen counted. The test material has distinguishable viral barrierproperties if the number of viruses is less than 100 for each sampletested. However, the number of viruses is preferably less than about 10,more preferably zero for each sample tested.

Viral Resistant Seam

The present invention is also directed to a low surface area reinforcedviral resistant seam for protective apparel. The low surface area seamis designed to provide adequate tensile strength and enhanced comfort tothe user. The method and apparatus for creating a comfortable reinforcedviral resistant seam includes an ultrasonic welding wheel which permitsmuch higher manufacturing speeds than other wheel designs.

FIG. 7 is a schematic illustration of an exemplary reinforced viralresistant seam 70 for an exemplary article of protective apparel (seee.g., FIG. 10). First and second webs 72, 74 are arranged to form asealed edge 76. A reinforcing strip 78 is placed on one side of thesealed edge 76 during an ultrasonic welding process, which is discussedin detail below. It will be understood that more than one reinforcingstrip 78 may be used for the seam 70 and that the location of the strip78 may vary. For example, the reinforcing strip 78 may be locatedin-between or on either side of the webs 72, 74. The welding site 79 isimmediately adjacent to the sealed edge 76 and preferably is within0.794-6.35 mm (1/32" to 1/4") of the sealed edge 76. Since the distalend 81 of the reinforcing strip 78 is not subject to the weldingprocess, it remains soft, pliable and comfortable for the wearer.

The webs 72, 74 and reinforcing strip 78 may be constructed from avariety of woven or nonwoven materials having a thermoplastic component,as discussed above. Other microporous films with desirable breathabilityand moisture vapor transmission rates include: oriented particle filmssuch as those described in U.S. Pat. No. 4,777,073, U.S. Pat. No.4,347,844, U.S. Pat. No. 5,176,953, and U.S. Pat. No. 5,317,035; colddense films made porous by hot and cold stretching such as thosedescribed in U.S. Pat. No. 5,013,439, U.S. Pat. No. 3,839,240, U.S. Pat.No. 3,426,754, U.S. Pat. No. 3,843,761, U.S. Pat. No. 3,801,404, andU.S. Pat. No. 3,801,692; and other thermally induced phase separatedfilms such as described in U.S. Pat. No. 4,867,881, U.S. Pat. No.4,539,256 and U.S. Pat. No. 4,519,909, all of which are herebyincorporated by reference.

FIG. 8 illustrates an alternate viral resistant seam 70' utilizing theviral barrier composites 48, 49. The spunbond web 22 of the viralbarrier composite 48 is arranged to engage the spunbond webs 22a on thetrilaminate composite viral barrier 49. The reinforcing strip 78 isarranged adjacent to the microporous membrane 24 on the bilaminate 48.The reinforcing strip may be a woven or non-woven web constructedpredominately from polypropylene fibers or a film. A 136 gram/ m² (4ounce/yard²) non-woven polypropylene web suitable for use as thereinforcing strip is available from Poly-Bond, Inc. under part number06525. It will be understood that a variety of other materials thermallybondable to the viral barrier composites 48, 49 may be suitable for thereinforcing strip 78.

In order to achieve a strong weld 79' along the seam 70', a portion ofthe bilaminate and trilaminate viral barrier composites 48, 49 and thereinforcing strip 78 are energized to a molten state by the ultrasonicwelding process, which will be discussed below. The molten thermoplasticmaterial flows around and adheres to the non-molten fibers of thespunbond nonwoven webs 22, 22a, 22b laminated to the microporousmembrane 24.

The optimum quantity of energy transmitted by the ultrasonic generatoris a function of dwell time under the ultrasonic welding wheel, the gapbetween the welding wheel and the ultrasonic generator, amplitude of theultrasonic generator and the mass and composition of the material beingwelded. For a given viral barrier film or composite, excess ultrasonicenergy at weld site may weaken the material. It is believed that areinforcing strip 78 thermally bondable with the bilaminate 48 andtrilaminate 49 provides additional material mass to the weld area thatdecreases the possibility that the microporous membrane 24, and itsviral barrier capabilities, will be degraded by the welding process.

FIG. 9A is a schematic illustration of an ultrasonic welding system 90suitable for forming viral resistant seam 70, 70'. Welding wheel 91 hasa cutting edge 92 immediately adjacent to a solid seal area 94. Thesolid seal area 94 preferably has a width "s" of approximately 1.524 mm(0.060"). The cutting edge 92 has a V-shape having an angle α ofapproximately 60°. An ultrasonic welding unit capable of operatingaccording to the present invention is available from SonobondCorporation of Westchester, Pa., under model number LM-920. It will beunderstood that a variety of commercially available ultrasonic weldingunits may be suitable for this purpose.

The critical dimension or gap 96 between the solid seal area 92 and anultrasonic generator 98 is a function of the thickness and compositionof the webs 72, 74 and the reinforcing strip 78, the amplitude ofoscillation and the rate at which the material passes under the weldingwheel 91. Additionally, wheel pressure must be adequate to cut whilewelding or produce an easily removable trim. Finally, the peak to peakamplitude of oscillation is generally in the range of gap. Specificexamples are set forth below.

It has been found that the welding speed also significantly impacts thesleeve seam tensile strength and the number of pinholes created. Slowerspeeds typically increase tensile strength and decrease pinholes. Slowerwelding speeds increase tensile strength and a higher amplitude alsotypically increases tensile strength. There appears to be an upper limitbeyond which the output amplitude can be set without creating excessivepinholes. It is believed that the transition takes place at an amplituderange above 0.0762 mm (0.004 inches).

For the seam 70' of FIG. 8 constructed of the viral barrier composites48, 49, the solid seal area 94 of the welding wheel 91 extrudes moltenpolypropylene into the spunbond fibers adjacent to the welding site 79'.The gap 96 between the solid seal area 94 on the welding wheel 91 andultrasonic generator 98 affects the degree to which the spunbond fibersnear the seam 70' are weakened, as well as how much molten thermoplasticmaterial is produced by the welding process. If the gap 96 is too small,the fibers near the weld area will degrade, thereby weakening the viralbarrier composites 48, 49 and the seam 70'. If the gap 96 is too large,not enough molten thermoplastic material will be produced and theresulting seam 70' will be weak.

FIG. 10 is an exemplary article of protective apparel 100 for which thepresent method and apparatus can be utilized. The protective apparel 100has a body portion 102 with a pair of sleeve attachment edges 104, 106to which an open end 108, 110 of first and second sleeve 112, 114 can beattached, respectively. It has been found that sleeve attachment seams116, 118 preferably have a tensile strength in excess of five pounds perinch. In the present exemplary embodiment, the sleeves 112, 114 may beconstructed of the trilaminate composite 49 to provide comfort and agreater base strength, while the body portion 102 may be constructedfrom a bilaminate composite 48 to minimize cost and weight. The averageseam strength of the present reinforced viral resistant seams 70, 70' istypically 7.5 pounds per inch and is in a range generally between 5.7 to9.3 pounds per inch, as will be discussed in the Examples detailedbelow. It will be understood that the present reinforced viral resistantseams 70, 70' may be used for any seams of the protective apparel 100.

Objects and advantages of this invention are further illustrated by thefollowing examples, but the particular materials and amounts thereofrecited in these examples as well as other conditions and details,should not be construed to unduly limit this invention. All materialsare commercially available except where stated or otherwise madeapparent.

EXAMPLES Example 1

A bilaminate was prepared by thermally point bonding a 0.0305 mmmicroporous membrane prepared as described in Example 9 of U.S. Pat. No.5,260,360 to Mrozinski et al. dated Nov. 9, 1993 except the blend ratioof materials was 62.5/1.5/2.5/33.5, PP/FCO/BLUE RED 8515 fromHoechst-Celanese, Charlotte, N.C./MO to a 33.9 g/m² polypropylenespunbond nonwoven web commercially available as Style No. 341, 33.9g/m², sky blue color from Poly-Bond, Inc., Waynesboro, Va. Theconditions for thermal point bonding the membrane are in Table 1. Themembrane was in contact with the heated smooth roll and the nonwoven webin contact with the heated pattern roll. The web width was approximately1.66 meters. The steel pattern roll had a diamond point bonding pattern.The point bonding represented approximately 20% bonding surface area,21.7 points/cm², and individual bond point size of 0.8 mm². Thebilaminates were tested for machine direction bond strength, porosity(Gurley), pinholes, viral barrier properties, and MVTR. The test methodsare described above and the test results are in Table 2. At least threetests were performed for each test method.

Comparison Example A

The bilaminate was prepared and tested as described in Example 1 usingthe conditions in Table 1. The test results are in Table 2. This examplerepresents the same conditions as Example 1 except an increase in thesmooth roll temperature which caused the bilaminate to increase bondstrength, lose porosity, and increase number of pinholes.

Example 2

The bilaminate was prepared and tested as described in Example 1 usingthe conditions in Table 1. The test results are in Table 2.

Comparison Example B

The bilaminate was prepared and tested as described in Example 1 usingthe conditions in Table 1. The test results are in Table 2. This examplerepresents the same conditions as Example 2 except a decrease in theroll temperatures and the subsequent decrease in bond strength.

Example 3

The bilaminate was prepared and tested as described in Example 1 usingthe conditions in Table 1, except the diamond point bonding representedapproximately a 21.6% bonding surface area, 51.0 points/cm², andindividual bond point size of 0.42 mm². The test results are in Table 2.

Example 4

The bilaminate was prepared and tested as described in Example 1 usingthe conditions in Table 1, except the diamond point bonding representedapproximately a 21.6% bonding surface, 51.0 points/cm², and individualbond point size of 0.42 mm². The test results are in Table 2.

Comparison Examples C and D

The bilaminate was prepared and tested as described in Example 1 usingthe conditions in Table 1, except the diamond point bonding representedapproximately a 21.6% bonding surface, 51.0 points/cm², and individualbond point size of 0.42 mm². The test results are in Table 2. Theseexamples represent the same roll temperatures and pressure as Example 4with a decrease in the line speed and the subsequent increase in numberof pinholes and increase in bond strength.

Example 5

Ten samples of the bilaminate was prepared and tested as described inExample 1 using the conditions in Table 1, except the diamond pointbonding represented approximately a 17-20 percent bonding surface. A 2meter wide calender that had a 1 mm crowned smooth roll was gapped byputting shimstock between the bearing housings of the rolls. Thisprovided a gap of approximately 2 mils between the rolls on the outer450-500 mm edges of the web. The outer 500 mm along one edge of thematerial that was tested and the test results are in Table 2.

Example 6

The bilaminate was prepared and tested as described in Example 1 usingthe conditions in Table 1, except the diamond point bonding representedapproximately a 15% bonding surface. A gap was set between the two steelrolls. The web width was approximately 0.5 meters. The test results arein Table 2.

                  TABLE 1                                                         ______________________________________                                               Pattern Roll                                                                            Smooth Roll                                                         Temperature                                                                             Temperature         Line Speed                               Examples                                                                             (°C.)                                                                            (°C.)                                                                            Pressure (N/mm)                                                                         (m/min.)                                 ______________________________________                                        1      145       140       15        52                                       A      143       150       15        52                                       2      148       146       10        67                                       B      135       130       10        67                                       3      151       142       15        52                                       4      135       135       50        100                                      C      135       135       50        65                                       D      135       135       50        30                                       5      135       130       0.0254 mm gap.sup.1                                                                     27                                       6      142       116       0.0254 mm gap.sup.1                                                                      9                                       ______________________________________                                         .sup.1 a gap was set between the rolls instead of using pressure to keep      the rolls together.                                                      

                  TABLE 2                                                         ______________________________________                                               Average                 Viral Barrier                                         Bond    Porosity Pinholes                                                                             (failed samples                                                                        MVTR                                         Strength                                                                              (Gurley) per no.                                                                              per samples                                                                            (g/m.sup.2 /24                        Examples                                                                             (N/cm)  (sec/50 cc)                                                                            samples                                                                              tested)  hrs)                                  ______________________________________                                        1      0.200      74.1.sup.1                                                                          0/9    1/27     7340                                  A      1.4     ∞  5/9    Not tested                                                                             --                                    2      0.159   140      0/9    0/33     --                                    B      0.025   134      0/9    Not tested                                                                             --                                    3      0.403    59       2/35  0/28     7674                                  4      0.123   116      1/3    Not tested                                                                             --                                    C      0.193   108      4/3    Not tested                                                                             --                                    D      0..298  120      8/3    Not tested                                                                             --                                    5      0.355   115      1/9    0/27     --                                    6      0.385    83      0/9    Not tested                                                                             --                                    ______________________________________                                         .sup.1 Microporous membrane had Gurley of approximately 60 sec/50 cc prio     to lamination.                                                           

Example 7

Trilaminates were prepared by thermally point bonding a 0.0305 mmmicroporous membrane prepared as described in Example 9 of U.S. Pat. No.5,260,360 to Mrozinski et al. dated Nov. 9, 1993 except the blend ratioof materials was 62.5/1.5/2.5/33.5, PP/FCO/BLU; RED 8515 fromHoechst-Celanese, Charlotte, N.C./MO to a 33.9 g/m² polypropylenespunbond nonwoven web commercially available as Style No. 341, 33.9g/m², sky blue color from Poly-Bond, Inc., Waynesboro, Va. Theconditions for bonding the membrane to the web are in Table 3. One webwas next to the heated smooth steel roll and the other web next to theheated pattern roll with the membrane between the two webs. The webwidths were approximately 1.66 meters. The steel pattern roll had adiamond point bonding pattern which represented approximately 20%bonding surface area, 21.7 points/cm², and individual bond point size of0.8 mm². The trilaminates were tested for machine direction bondstrength, pinholes, viral barrier properties, and MVTR. The test methodsare described above and the test results are in Table 4.

Example 8

The trilaminate was prepared and tested as described in Example 7 usingthe conditions in Table 3, except the diamond point bonding representedapproximately a 21.6% bonding surface, 51.0 points/cm², and individualbond point size of 0.42 mm². The test results are in Table 4.

                  TABLE 3                                                         ______________________________________                                                Pattern Roll                                                                             Smooth Roll                                                        Temperature                                                                              Temperature                                                                             Pressure                                                                             Line Speed                                Examples                                                                              (°C.)                                                                             (°C.)                                                                            (N/mm) (m/min)                                   ______________________________________                                        7       150        150       10     37                                        8       142        155       20     52                                        ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                               Average Average                                                               Bond    Bond                                                                  Strength                                                                              Strength        Viral Barrier                                         Pattern Smooth  Pinholes                                                                              (number of                                            Roll    Roll    (number per                                                                           failures per                                                                          MVTR                                   Exam-  Side    Side    number of                                                                             number of                                                                             (g/m.sup.2 /24                         ples   (N/cm)  (N/cm)  samples)                                                                              samples)                                                                              hrs)                                   ______________________________________                                        7      0.123   0.173   0/9     1/16    --                                     8      0.215   0.292   3/70    2/20    7330                                   ______________________________________                                    

Example 9

Seams were formed as illustrated in FIG. 8 using a trilaminate of amicroporous membrane prepared as described in Example 9 of U.S. Pat. No.5,260,360 to Mrozinski et al. dated Nov. 9, 1993, except the blend ratioof materials was 62.5/1.512.5/33.5, PP/FCO/BLUE RED 8515 (available fromHoechst-Celanese, Charlotte, N.C.)/MO, thermally point bonded betweentwo layers of a spunbond nonwoven polypropylene web commerciallyavailable as Style No. 341, 33.9 g/m², sly blue color from Poly-Bond,Inc., Waynesboro, Va., a bilaminate of the microporous membrane materialthermally point bonded to one layer of the spunbond nonwovenpolypropylene web so that the nonwoven side was in contact with thenonwoven of the trilaminate, and a reinforcing strip of a 135.6 g/m² (4oz./sq. yd.) spunbond nonwoven polypropylene web commercially availableas "Style: 06525 Industrial Spunbonded Polypropylene" from Poly-Bond,Inc. The thermal point bond conditions for the bilaminate and thetrilaminate are in Table 5. These laminates were combined by ultrasonicwelding using an ultrasonic welding unit commercially available as ModelNumber LM-920 from Sonobond Corporation, Westchester, Pa. with a weldingwheel as shown in FIG. 9A. The welding wheel speed dial setting was 5,the horn speed setting was 5, the output setting was 5 and the pressuresetting was 0.414 MPa (60 psi). The gap between the solid seal area andan ultrasonic horn is in Table 6. These settings produces seams withadequate tensile strength at welding speeds of up to 12.31 meters/minute(40 feet/minute). The weld tensile strength was determined using amodification of ASTM Test Method D5035-90 using an "Instron Model 1122Tensile Tester" from Instron Corporation, Canton, Mass. The gage lengthwas set at 5.08 cm (2 inches) and the crosshead speed was 304 mm/min.The seams were prepared so that the seam was tested in the directionperpendicular to the machine direction (cross machine direction). Theresults of the weld tensile strength test are shown in Table 6.

                  TABLE 5                                                         ______________________________________                                        Thermal Point Bond Conditions for:                                                             Bilaminate                                                                           Trilaminate                                           ______________________________________                                        Pattern Roll Temperature (°C.)                                                            148      150                                               Smooth Roll Temperature (°C.)                                                             140      150                                               Pressure (Newton/millimeter)                                                                      10       20                                               Line Speed (meters/minute)                                                                        67       50                                               ______________________________________                                    

Comparison Example G

Seams were formed using the same bilaminate and trilaminate describedfor Example 9 without the reinforcing strip. The laminates were combinedby ultrasonic welding as described in Example 9 except the welding wheelused is shown in FIG. 9B and the gap between the welding wheel and thehorn was decreased to compensate for the different thickness without thereinforcing strip. The weld tensile strength was tested as in Example 9and the results are shown in Table 6.

Example 10

Seams were formed using two bilaminates between two reinforcing stripsdescribed for Example 9. The laminate fabrics and strip were combinedwith the nonwoven sides of the laminate together by ultrasonic weldingas described in Example 9 except the welding wheel used is shown in FIG.9A and the gap between the welding wheel and the horn was increased tocompensate for the different thickness of the laminates and theadditional reinforcement strip. The weld tensile strength was tested asin Example 9 except the seams were prepared so that the seam was testedin the machine direction and results are shown in Table 6.

Comparison Example H

Seams were formed using two bilaminates without the reinforcing stripdescribed for Example 9 using the welding wheel of FIG. 9B. The laminatefabrics were combined by ultrasonic welding as described in Example 9except the gap between the welding wheel and the horn was decreased tocompensate for the different thickness of the laminates without thereinforcing strip. The weld tensile strength was tested as in Example 9,except the seams were prepared so that the seam was tested in themachine direction. The results are shown in Table 6.

Example 11

Seams were formed using two polyethylene bilaminates commerciallyavailable as "Daltex CN4 Polyethylene Barrier Fabric" from Don and LowNonwovens Ltd., Forfar, Scotland and a reinforcing strip made of 2layers of clear, liner grade polyethylene bag material commerciallyavailable from Polar Plastics, Oakdale, Minn. The surface of the bagmaterial was cleaned by wiping with a hexane soaked paper towel beforewelding. The laminate fabrics and reinforcing strip were combined byultrasonic welding as described in Example 9 except the welding wheelused is shown in FIG. 9B and the gap between the welding wheel and thehorn was adjusted to compensate for the different thickness of thelaminates and the strip. The weld tensile strength was tested as inExample 9 and the results are shown in Table 6.

Comparison Example I

Seams were formed using two bilaminates without the reinforcing stripdescribed for Example 11. The laminate fabrics were combined byultrasonic welding as described in Example 9 except the welding wheelused is shown in FIG. 9B and the gap between the welding wheel and thehorn was decreased to compensate for the different thickness of thelaminates without the reinforcing strip. The weld tensile strength wastested as in Example 9 and the results are shown in Table 6.

Example 12

Seams were formed using two 30 grams per square yard nylon/rayonnonwoven diskette liners commercially available as "#9245" from Veratec,Walpole, Mass. and a reinforcing strip made from one layer of apolyester film commercially available as "PP2500 Transparency Film" from3M, St. Paul, Minn. The nonwoven fabrics and strip were combined byultrasonic welding as described in Example 9 except the welding wheelused is shown in FIG. 9B and the gap between the welding wheel and thehorn was adjusted to compensate for the different thickness of thelaminates and the strip. The weld tensile strength was tested as inExample 9 and the results are shown in Table 6.

Comparison Example J

Seams were formed using the two nonwoven fabrics without the reinforcingstrip described for Example 12. The laminate fabrics were combined byultrasonic welding as described in Example 9 except the welding wheelused is shown in FIG. 9B and the gap between the welding wheel and thehorn was decreased to compensate for the different thickness of thelaminates without the reinforcing strip. The weld tensile strength wastested as in Example 9 and the results are shown in Table 6.

                  TABLE 6                                                         ______________________________________                                                        Total   Weld                                                                  Thick-  Tensile                                                                             Standard                                                Gap     ness    Strength                                                                            Deviation                                                                            Number of                                Examples                                                                              (mm)    (mm)    (N/cm)                                                                              (N/cm) Samples Tested                           ______________________________________                                        9       0.0635  0.889   17.14 4.15   20                                       Comp. G 0.0508  0.406   12.91 2.94   20                                       10      0.1461  1.270   20.31 1.75   25                                       Comp. H 0.0381  0.305   17.51 2.35   30                                       11      0.0762  0.508    4.71 0.84   22                                       Comp. I 0.0254  0.406    3.15 0.61   21                                       12      0.1016  0.483    1.10 0.35   24                                       Comp. J 0.0254  0.356    0.44 0.25   20                                       ______________________________________                                    

In general, reinforced seam welds are stronger than the same weldwithout reinforcing strips.

Although the invention has been described with respect to specificpreferred embodiments, it should be appreciated that other embodimentsutilizing the concept of the present invention are possible withoutdeparting from the scope of the invention. The invention, for example,is not intended to be limited to the specific webs disclosed in thepreferred embodiments; rather the invention is defined by the claims andequivalents thereof.

What is claimed is:
 1. A viral barrier composite comprising a breathablethermoplastic film thermally bonded on at least one side thereof to abreathable thermoplastic web, the viral barrier composite having viralbarrier properties that permit less than 100 viruses to pass accordingto ASTM Method ES 22-1992, a moisture vapor transmission rate of atleast 700 g/m² /24 hours and a bond strength between the thermoplasticfilm and breathable thermoplastic web of at least 0.07 N/cm.
 2. Theviral barrier composite of claim 1 wherein the thermoplastic filmcomprises a thermoplastic polymer and a water- and oil-repellentfluorochemical compound that forms a microporous membrane witholeophobic and hydrophobic properties.
 3. The viral barrier composite ofclaim 2 wherein the microporous membrane comprises polypropylene.
 4. Theviral barrier composite of claim 1 wherein air permeability expressed asGurley porosity comprises less than 1000 seconds/50 cc.
 5. The viralbarrier composite of claim 1 wherein air permeability expressed asGurley porosity comprises less than 500 seconds/50 cc.
 6. The viralbarrier composite of claim 1 wherein the thermoplastic web comprises abonded spunbond nonwoven polypropylene web.
 7. The viral barriercomposite of claim 1 wherein less than 50 viruses are permitted to passaccording to ASTM Test Method ES 22-1992.
 8. The viral barrier compositeof claim 1 wherein less than 10 virus are permitted to pass according toASTM Test Method ES 22-1992.
 9. The viral barrier composite of claim 1wherein no virus are permitted to pass according to ASTM Test Method ES22-1992.
 10. An article of protective apparel constructed from the viralbarrier composite of claim
 1. 11. The article of protective apparel ofclaim 10 having at least one reinforced viral resistant seam, the viralresistant seam comprising:a first viral barrier composite having a firstattachment edge; a second viral barrier composite having a secondattachment edge arranged with the first composite viral barrier to forma common seam edge extending along the first and second attachmentedges; at least one reinforcing strip extending along the common seamedge constructed from a thermoplastic material thermally bondable withthe first and second viral barrier composite; and an ultrasonic weldbonding the first and second attachment edges and the reinforcing stripgenerally extending along a sealed edge to form the reinforced viralresistant seam.
 12. The viral resistant seam of claim 11 wherein theultrasonic weld comprises a weld line offset less than 1.0 cm from thesealed edge.
 13. A viral barrier composite comprising a breathablethermoplastic microporous membrane thermally bonded on at least one sidethereof to a breathable thermoplastic nonwoven web, the viral barriercomposite having viral barrier properties that permit less than 100viruses to pass according to ASTM Method ES 22-1992 and a bond strengthbetween the thermoplastic microporous membrane and the breathablethermoplastic nonwoven web of at least 0.07 N/cm.
 14. The viral barriercomposite of claim 13 wherein less than 50 viruses are permitted to passaccording to ASTM Test Method ES 22-1992.
 15. The viral barriercomposite of claim 13 wherein the microporous membrane comprises athermoplastic polymer and a water- and oil-repellent fluorochemicalcompound that forms a microporous membrane with oleophobic andhydrophobic properties.
 16. The viral barrier composite of claim 13wherein the thermoplastic microporous membrane and the breathablethermoplastic nonwoven web comprise polypropylene.